1. Field of the Invention
The present invention relates to laser material processing, and more specifically, it relates to precision micromachining with lasers.
2. Description of Related Art
Laser machining has found expanded use in automobile, aerospace, and electronics industries. For example, lasers are used in sheet metal cutting, drilling, and milling. In microelectronics, lasers are employed to scribe wafers, trim passive film elements, and obtain alloy p-n junctions of semiconductors. The advancements of laser machining are mainly due to the possibility of making small and unique structures that are difficult to achieve with conventional methods, and its applicability to traditionally hard-to-work materials such as ceramics, glass, and composite materials. Despite the advantages of laser machining, to date the introduction of precision laser micromachining to industry has been slowed by the lack of a well designed system.
Laser drilling has been widely used in industry because of its high production rate, capacity for rapidly varying hole size, and the ability to drill holes at shallow angles and in traditionally hard-to-work materials such as ceramics and composite materials. However, material removal based on conventional CO.sub.2 or YAG lasers is primarily through melt expulsion which leads to poor dimensional control, a sizable recast layer, and microcracks on the hole sidewalls. The strong plasma-beam interaction at infrared (IR) wavelengths also makes the material removal during laser drilling less controllable. Furthermore, the reduced ability to focus the IR laser beam makes it more difficult to produce micron-sized holes with large aspect ratios (i.e., hole depth to diameter).
Conventional laser machining using high-power CO.sub.2 and YAG laser systems are typically characterized by rough machining kerf, existence of recast layer and large heat affected zone, and relatively large feature size. As a result, these systems are seldom used in precision micromachining.
A more sophisticated laser system with increased processing control is therefore desired.